Urologist-level variation in androgen deprivation therapy intensification in patients with metastatic hormone-sensitive prostate cancer: A retrospective, population-based cohort study in Ontario, Canada.

59 Background: Guidelines recommend androgen-deprivation therapy (ADT) intensification for individuals with de novo metastatic hormone-sensitive prostate cancer (mHSPC). Urologists frequently initiate ADT and influence early treatment decisions, yet the extent to which variation in intensification reflects physician practice versus patient factors remains unclear. Methods: We identified all patients diagnosed with de novo mHSPC and initiated on ADT by urologists in Ontario, Canada (2015–2022). For each urologist, we calculated the annual number and proportion of patients receiving treatment intensification. Intensification was attributed to the urologist if they either prescribed it directly or referred the patient to another specialist who subsequently intensified therapy, to capture appropriate referral practices. Multilevel logistic regression models clustered at the physician level were fit, and the variance partition coefficient (VPC) was used to estimate the proportion of variation in treatment intensification attributable to physician-level effects, adjusting for patient- and physician-level covariates. Caterpillar plots were constructed to visualize physician-specific random intercepts for ADT intensification. Results: The analytic cohort included 332 urologists treating 3871 patients. Overall, physicians intensified therapy for an average of 23% of their patients (median 21%, IQR 0–33%). Descriptive yearly analyses showed a steady rise in intensification: mean proportion per urologist increased from 15% in 2016 to 59% in 2022. In the complete cohort, physician-level clustering explained only 4.6% of variation in treatment intensification, with most variation attributable to patient characteristics. In a contemporary sub-cohort (2020–2022), physician clustering explained a somewhat larger share (VPC 7.8–8.5%). There was wide heterogeneity in physician-specific intercepts, with most urologists clustering around the null effect but a long tail of higher-intensifying physicians. Conclusions: From 2015–2022, ADT intensification among patients initiated on therapy by urologists rose substantially. Most variation was explained by patient factors, though physician influence became more apparent in later years as early adopters drove uptake. These findings imply that accelerating equitable adoption of intensification may require system-level supports and targeted efforts to bring later adopters in line with evolving standards.